A Genetic Census of America

Using AncestryDNA results from over a quarter million people, the AncestryDNA science team set out to perform a “genetic census” of the United States: a survey of the U.S. using only DNA.

Where did the ancestors of today’s Americans come from? Do Americans in the Midwest hail from similar places of the world as in the Northeast, or as in the South?

Average amount of the given ethnicity (indicated in the drop-down menu) among AncestryDNA customers born in each U.S. state. If a state is dark green, it has a higher average (see key in lower left corner). Hovering over a state reveals the average amount of that ethnicity in the state (as a decimal).
Plot Source Attribution: googleVis-0.4.7, R version 2.15.1 (2012-06-22)

So to start, AncestryDNA estimated the genetic ethnicities of over 250,000 U.S. customers* as percentages in 26 regions across the world. These percentages show where a person’s ancestors may have lived hundreds to thousands of years ago. People of the United States, a nation settled by immigrants, often have a surprising diversity of ethnic backgrounds and collectively have ancestors who lived nearly all over the globe.

We then explored the spatial distribution of customers’ ethnicities across the 50 states – using maps to visualize where in the U.S. we often find people of different ethnicities.

Take a look at our maps of the U.S. above, one map for each of the 26 ethnicities AncestryDNA currently tests for. For every state, a map shows the average percentage of a particular ethnicity among all customers born there. If a state is dark green, it means that people there often have more of that ethnicity than in other states.

As you scroll through the maps using the drop-down menu, find a genetic ethnicity that has a high average in your state. Does it match with what you know about your ethnicity and the immigration of your ancestors to the U.S.?

Solely using ethnicity estimated by DNA, these maps reveal spatial patterns that are telling of the ancestral origins of present day Americans: where they came from and where they eventually settled.

CHAIN MIGRATION

“Chain migration” was a common strategy for many groups immigrating to the United States. Often, one family member would journey to the new land funded by family savings. Once there, they found employment, helping to pay for other relatives to make the same journey. This new wave of immigrants often lived with the sponsoring relative as they earned money for even more members of their family and community to join. As a consequence, families and friends ended up living in close proximity, and if they moved to another area of the U.S., often did so as a group. If these communities continued to live in the same region of the U.S. over many generations, you can begin to imagine how individuals of particular ethnicities might end up clustering together. That’s what we see in our maps.

SCANDINAVIAN ETHNICITY

For example, let’s look at the Scandinavian map. Scandinavian immigrants – from Sweden, Norway, and Denmark – tended to settle in the upper Midwest where geography, culture, and local economics felt familiar to life in the old country.

On the map, these are the greenest regions: the states with the highest amounts of Scandinavian ancestry. In other words, DNA also suggests localized migration of individuals of Scandinavian origin to North Dakota, Minnesota, and neighboring states, with little migration to other U.S. regions. History agrees with genetics!

IRISH ETHNICITY

Look at the Irish ancestry map as another example. The highest statewide averages are concentrated in Massachusetts and other states in the Northeastern U.S. – where many Irish immigrants, forced to leave their homes and lands, settled in the 19th century. Growing numbers of Irish that arrived after the 1820s were often poor and common laborers, and took jobs in the construction of buildings, canals, roads, and railways in cities in the eastern United States.

Many of these cities still show the highest average amounts of Irish ethnicity in the U.S. today! DNA affirms that many descendants of Irish immigrants still live where their ancestors initially settled – in the Northeast.

GREAT BRITAIN AND WESTERN EUROPE ETHNICITY

If you look at the maps for Great Britain and Europe West, you see that other ancestries are more widespread across the whole country. Leading up to the Boston Tea Party and the Declaration of Independence in 1776, large numbers of Europeans arrived in what is now the U.S., in some cases to escape religious persecution. While there were subsequently many waves of immigration, individuals primarily from Western Europe and Great Britain were our first Americans.

That we see British ancestry in many people of the U.S. may be evidence of the long history of individuals from Great Britain migrating to the United States, and far and wide across those states.

NATIVE AMERICAN ETHNICITY

Finally, other patterns in the ethnicity maps reveal less about immigration, and more about America’s native peoples. Take a look at Native American ancestry, which is present in high amounts in people born in New Mexico and other Southwestern states – a signal of both the large Native American and Latino populations that live there. And while Polynesian ancestry is nearly absent across the entire continental United States, it has a high average in Hawaii. Genetics confirms that most native Hawaiians live in – you guessed it – Hawaii.

With that context, take another look through the maps. What other patterns surprise you? Which ones don’t?

In most cases, you’ll find that the genetics lines up neatly with history. This is pretty remarkable considering that we haven’t used any information about history or one’s self-identified ethnicity (though equally significant in defining one’s heritage) to make these maps. DNA from all 50 states can tell us a great deal about the family histories and stories of the people within them.

Just over a decade ago, the very first human genome was sequenced. Today, from aggregated results of over a quarter million AncestryDNA customers, we’re deciphering the genetic information that individually and collectively holds the secrets of individuals’ family histories, our nation’s history, and the history of the whole human family.

* All customers in this study consented to participate in scientific research.

Julie has been a population geneticist at AncestryDNA since May 2013. Before that, Julie received her Ph.D. in Biology and M.S. in Statistics from Stanford University, where she studied genetic data from human populations and developed computational tools to answer questions about population history and evolution. She also spent time collecting and studying DNA using spit-collection tubes like the ones in an AncestryDNA kit. Julie likes to spend her non-computer time enjoying the outdoors – hiking, biking, running, swimming, camping, and picnicking. But if she’s inside, she’s baking, drawing, and painting.

10 Comments

You company may have done 250,000 but not one of them were mine. I have sent in three kits and yet not one has been processed for me. Yet the three other kits for three other people sent in at the same time by me have all been processed.

Very interesting and informative article. We have now had 6 family members do the DNA testing: my sister and I, my son, his wife, and oldest male child, and my oldest granddaughter from my daughter. The results were interesting. We knew Finnish would be included on my side due to my mother’s parents coming from there. Knowing Finland’s history, the Scandinavian genes were not a surprise. Tracing my father’s ancestry did add to Europe West and Great Britain. Having Irish genes and some others were a big surprise! It was a great experience, and I am mapping our ethnicities to see where commonalities occur. Hoping to add others to our DNA test list.

Hi Gary, thank you for your interest. Those numbers are the average amount of Scandinavian ethnicity in each state, averaged over all AncestryDNA customers born there. So in your example, North Dakota has an average ethnicity of 29.8%. There is now a caption underneath the map to make this more clear.

In terms of Irish, it’s a common misconception that Irish arrived in the 19th century, when in fact they were here in the early 1600’s. I’m Irish – grew up in Ireland – and 65% of my 2,000+ genetic relatives live in the US South.

Hi Paul, you are correct in that there were multiple waves of Irish immigration to the United States. While see the highest average Irish ethnicity in the northeastern United States, likely due to 19th century immigration, Irish ethnicity is not absent from other areas of the United States. This includes states of the southern U.S., where average Irish ethnicities are often above 15%.

Hi Michel, thank you for your comment. Germany is primarily represented as part of Europe West, though people with deep roots in Germany may also have trace amounts of Europe East ethnicity. We do not test for Canadian ancestry, since as you point out, individuals from many parts of the world settled in Canada. Indigenous Canadian heritage, on the other hand, would show up as Native American ethnicity.

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